<p>Small-scale fill dams, known as TAMEIKE, are typically constructed in valleys or on steep slopes. These dams occasionally serve the secondary function of temporarily damming debris flows and large quantities of sediment from upstream, thereby protecting downstream areas. However, owing to the recent increase in the frequency and intensity of torrential rain disasters, a rapid increase is observed in the number of cases in which TAMEIKE dams are decommissioned to mitigate embankment failure and protect downstream residents. In such instances, a section of the embankment is excavated into a V-shape (V-excavation) down to the base level, thereby eliminating the water storage capacity. The excavation of the embankment is likely to increase the risk of debris flows reaching downstream unimpeded; however, limited studies have been conducted on the damming effect of V-shaped open-cut embankments on debris flows. Consequently, flume model tests were conducted to investigate the damming effects of open-cut embankments. In these experiments, ceramic beads and wooden sticks were utilized to simulate debris flows, and the weight of debris flow dammed inside the embankment was assessed for each material across various open-cut geometries and positions. This study provides valuable foundational knowledge regarding the damming effect of V-shaped open-cut embankments on debris flows, an area that has been scarcely investigated. Notably, the findings indicate that slightly elevating the open-cut surface above the base, thereby enabling water storage, significantly enhances the damming effect. This result has important practical implications for dam design and flood mitigation.</p>